chore(brand): rename the product to ReplyPier

The upstream project name is gone from code, assets, docs and build
output: brand strings, domains (replypier.site and its app/api/docs/help
subdomains), env prefixes, image and network names, the widget's public
JS API (window.ReplyPier, replypierId/BaseUrl/Config/Token), CSS tokens
(--rp-*), file and directory names, and the WordPress plugin package.

- widget loader is now webclient/replypier.min.js; both bundles rebuilt
  from source (backend/assets/widget.{js,css}, frontend/public/webclient)
- NOTICE, llms.txt, CONTRIBUTING, HELP_CENTER_INFRA and config.dev.js
  rewritten rather than string-swapped; the demo config no longer ships
  the previous vendor's Firebase/Razorpay/Google keys
- new migration replypier_ai_model_001 adds REPLYPIER to the managed
  AIModelType and rewrites pre-rename rows
- local compose project, database, role and volume renamed; LOCAL_DEPLOY
  documents carrying the old local data over

backend/tests/api/test_help_center_api.py

@@ -1,5 +1,5 @@
 """
-Copyright 2024-2026 ChatterMate
+Copyright 2024-2026 ReplyPier
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -152,7 +152,7 @@ def test_faq_seo_fields_round_trip(client):
     created = client.post(f"{BASE}/faqs", json={
         "question": "What does it cost?", "answer": "From $19.",
         "slug": "Pricing & Plans!", "meta_title": "Pricing",
-        "meta_description": "What ChatterMate costs.",
+        "meta_description": "What ReplyPier costs.",
     })
     assert created.status_code == 201
     # A hand-typed slug is normalized the same way a generated one is.
@@ -163,7 +163,7 @@ def test_faq_seo_fields_round_trip(client):
     updated = client.put(f"{BASE}/faqs/{faq_id}", json={"slug": "our-pricing"})
     assert updated.json()["slug"] == "our-pricing"
     # Untouched overrides survive a partial update.
-    assert updated.json()["meta_description"] == "What ChatterMate costs."
+    assert updated.json()["meta_description"] == "What ReplyPier costs."
 
 
 def test_faq_slug_is_deduped_but_stable_for_its_own_row(client):